One of them, Mike Ash said he thought it was "wrong of Apple" to presume that he would indemnify them. He said the email was "presumptuous".

And, in a blogpost entitled I Do Not Agree To Your Terms, he took issue with the requirement to opt out.

He wrote: "Let me get this straight, Apple: you send me an email outlining the terms under which you will redistribute my content, and you will just assume that I agree to your terms unless I opt out?

"You're going to consider me bound to terms you just declared to me in an email as long as I don't respond? That's completely crazy. You don't even know if I received the email!"

Image copyrightGetty ImagesImage caption
Tim Cook appeared onstage at the WWDC conference, where the news app was announced earlier this month

According to Graham Hann, the head of technology, media and communications at the law firm Taylor Wessing, the terms of the deal are broadly in line with industry standards - except the requirement to opt out.

"The content of the notice is not unusual, although it has deliberately been dumbed down, possibly for clarity," he told the BBC.

"However, the optout approach is very unusual and I don't see how the notice could form a binding contract without a positive reply.

"Apple clearly wants to launch with as much content as possible and has taken this risk-based approach. Some publishers may object and even threaten to sue.

"However, I think it would be hard to claim damage beyond a reasonable royalty fee."

Human curation

Apple will place the publishers' content via a publicly available RSS feed, which sends any updates to a blog or website to the host - in this case, Apple News.

Publishers make these feeds publicly available voluntarily.

After announcing the launch of the app, the company began advertising for editorial staff to work on it, indicating that it would be curated by a human editor, rather than an algorithm.

The news app is categorised as part of the firm's marketing department.

It is due to be launched with the latest operating system update - iOS9 - later in 2015.

Apple also announced at the WWDC developers' conference that it was launching a music streaming app that would include the user's music video library, as well as an internet radio station and a way for artists to share unreleased tracks.